1. Field of the Invention
The present invention relates to an image detecting device and readout exposure apparatus therefor, and more particularly to a readout exposure apparatus for reading out image data stored on an image detecting device by scanning aforementioned image detecting device with readout electromagnetic radiation.
2. Description of the Related Art
There have been known in the field of medical radiology image readout systems employing photoconductive members such as panels composed of a-Se, etc., which are sensitive to X-rays, employed as light sensitive members or electrostatic recording members for improving diagnostic performance and reducing the quantity of radiation a subject is bombarded with, wherein an electrostatic recording member is irradiated by X-ray, etc. radiation carrying radiation image data, a latent image charge carrying the radiation image data is placed on the electrostatic recording member, after which, by scanning the light sensitive member with a laser beam a current is produced therein, and by detection of that current by the flat electrodes or stripe electrodes on both sides of the light sensitive member, the electrostatic latent image carried by the latent image charge, that is, the radiation image data (see for example, U.S. Pat. Nos. 4,176,275, 5,440,146, and 5,510,626, xe2x80x9cA Method of Electronic Readout of Electrophotographic and Electroradiographic Imagesxe2x80x9d; Journal of Applied Photographic Engineering, Volume 4, Number 4, Fall 1978 pp178-182 (hereinafter referred to as 1), etc.).
In the systems described in U.S. Pat. Nos. 4,176,275 and 5,510,626, and document 1, a narrow line of light formed by the expansion of a beam output by an argon laser is focused onto the light sensitive member by a cylindrical lens in the apparatus, so that the narrow line of light is mechanically deflected and scanned over the light sensitive member. The stored electrostatic image is readout in a linear manner by a plurality at line electrodes arranged in a stripe pattern.
In addition, a readout system for reading out radiation image data stored on an electrostatic recording member comprising a first photoconductive layer transparent to recording radiation, a recording photoconductive layer that exhibits conductivity upon irradiation thereof by recording radiation, a charge transport layer that acts substantially as an insulator to charges in the same polarity as that of the charge placed on the first photoconductive layer and substantially as a conductor to charges in the reverse polarity thereto, a readout photoconductive layer that exhibits conductivity upon irradiation thereof by readout radiation, and a second photoconductive layer, which is transparent to readout radiation, superposed one on the other in that order, has been proposed in Japanese Patent Application No. 10(1999)-232824.
According to the readout apparatus disclosed in Japanese Patent Application No. 10(1999)-232824, an electrostatic recording member is scanned by readout electromagnetic radiation generated by a light source, and the electrostatic image stored in the electrostatic recording member is readout. A line-shaped exposure light means, a laser beam scanning means, etc. have been proposed for use as the readout exposure apparatus, which is a light source for emitting readout electromagnetic radiation. Further, a plurality of light emitting points arranged in a line, etc. has been proposed for use as a line-shaped exposure apparatus.
When such a line-shaped exposure means having a plurality of light emitting points arranged in a line is used as the readout exposure apparatus of the detecting device described above, the light emitting points can be considered to be in a relationship of a one-to-one correspondence with the irradiation points (readout pixels) on the detecting device. However, in such a system, when on of the light emitting points malfunctions and a decrease in the quantity of light output is thereby decreased, because the exposure light for the corresponding irradiation point on the detection device is insufficient, a malfunction of only one of the light emitting points from among the plurality of light emitting points is regarded as a malfunctioning of the light source. In addition, if there is inconsistency between light emitting points with regard to the quantity and angle at which light is emitted, as a result, a problem arises in that artifacts occur in the images.
The present invention has been developed in consideration of the circumstances described above, and it is a main objective of the present invention to provide a readout exposure apparatus in which the frequency of light source malfunction is reduced and inconsistencies in exposure are controlled.
The readout exposure apparatus for reading out data recorded on an image detecting device by scanning said image detecting device with readout electromagnetic radiation according to the present invention comprises an exposure light source having a plurality of light emitting points arranged in a line, a first optical means, which has an optical member for focusing said electromagnetic radiation through an opening having a slit, that spatially filters the electromagnetic radiation emitted from each of the light emitting points of the exposure light source, wherein the electromagnetic radiation emitted from each light emitting point passing through the first optical means enters the image detecting device after having been dispersed along the lengthwise direction of said exposure light source, whereby each portion of the image detection device is simultaneously exposed to the electromagnetic radiation emitted from multiple light emitting points from among said plurality of light emitting points.
The expression xe2x80x9ceach portion of the image detecting devicexe2x80x9d refers to each portion of the image detecting device included exposure zone.
Note that it is desirable that the slit opening extend in the lengthwise direction of the exposure light source, and that the optical member focus the electromagnetic radiation emitted from each light emitting point in the direction perpendicular to the lengthwise direction of the exposure light source.
In addition, it is desirable that a second optical means be provided for focusing the electromagnetic radiation passing through the first optical means in the direction perpendicular to the lengthwise direction of the exposure light source.
Note that the optical member can be a SELFOC lens and the second optical means a cylindrical lens, or both the optical member and the second optical means can be cylindrical lenses.
Note that aforementioned exposure light source can be a plurality of LED or LD chips arranged in a line, or it can be an LED or LD array.
Note that the image detection device can be an electrostatic recording member that records image data as an electrostatic latent image, and by scanning thereof by readout electromagnetic radiation a current corresponding to aforementioned electrostatic latent image can be generated, or it can be a stimulable phosphor sheet that cumulatively stores image data and emits a stimulated emission corresponding to aforementioned image data upon irradiation thereof by readout electromagnetic radiation.
Note that the referent of the expression xe2x80x9celectromagnetic radiationxe2x80x9d includes all wavelengths of light in the visible range, infrared range, etc., and for cases in which the image detecting device is an electrostatic recording member, can be any wavelength by which the xe2x80x9celectrostatic latent imagexe2x80x9d can be readout, and for cases in which the image detecting device is a stimulable phosphor sheet, any wavelength of light that causes stimulated emission to be emitted can be used as the stimulating light. This holds true for that described below.
As described above in the description of the prior art, a light source comprised of a plurality of light emitting points arranged in a line can be used as the aforementioned readout exposure apparatus. If the light source is formed of N light emitting points, if each light emitting point corresponds to an irradiation point on the detecting device in a one-to-one relation, and if the apparatus is defined as being in a state of malfunction when an individual light emitting point malfunctions, then the malfunction rate of the apparatus is expressed as equal to (the malfunction rate of each single light emitting point)xc3x97N, where xe2x80x9cxxe2x80x9d stands for a multiplication sign.
In addition, if the inconsistency in the quantity of light emitted by the light emitting points in this case is A % (where the area irradiated by each exposure point is the same anywhere), the rate at which inconsistencies occur in the exposure of each point on the detecting device is also A %.
However, according to the readout exposure apparatus of the present invention, because the detecting device is uniformly exposed by any number of exposure light emitting points, for example, M points (Mxe2x89xa72), if an individual point among those points malfunctions and ceases emitting light, the reduction in the quantity of exposure light is only 1/M, and because the malfunctioning of a single light emitting point does not directly result in a malfunctioning of the entire apparatus, the rate of malfunction can be reduced compared to the case described above.
In addition, even if the rate of the inconsistency in the quantity of light emitted from the light emitting points is A % (where the area irradiated by each exposure point is the same anywhere), because each point on the detecting device is irradiated by M light emitting points, the inconsistency in the quantity of exposure light is, on average, A/M %, which is a reduction compared to the above described case.
That is to say, the rate of malfunction and the inconsistency in the quantity of the exposure light emitted are reduced in the readout exposure apparatus according to the present invention, and readout of an image having a reduced number of artifacts occurring of artifacts can be obtained.
Further, because readout exposure apparatus according to the present invention exhibits a level of performance and serviceable life span that is the same or better than conventional readout exposure apparatus, the life required for conventional light emitting elements is no longer necessary, and the specification regarding the inconsistency in the quantity of light emitted is not as stringent as it was for conventional light emitting elements. Accordingly, yield can be improved.
Still further, by providing a first optical means for spatially filtering the electromagnetic radiation emitted from each light emitting point of the exposure light source, the quality of the electromagnetic radiation emitted from each light emitting point can be improved.